Home prices across the U.S., aided by two Florida metropolitan areas,ended 2012 with the largest gain since the housing market began to crash, according to figures released Tuesday by S&P Dow Jones.The S&P/Case-Shiller Home Price Indices, a leading barometer of U.S. home prices, revealed the best year-over-year gain, through December, in home prices since July 2006. Its 10-city index showed prices up 5.9 percent, while the 20-city composite showed annual returns of 6.8 percent.